We have always carried freshwater in our tank regardless if destination has water readily available, there's a few reasons why we do. Manufacturer's that advise not to fill your tanks more than likely install sub-grade tanks prone to fail, or are poorly designed to keep them from falling out, defeating the very purpose of purchasing an RV.
With our toyhauler we can carry well over 1K# of fluids which we did occasionally, never feared one of our tanks would ever fall out or crack, we did verify that they were well secured by the factory. After a few decades of RVing, and from TT to Class A, we continue to bring our own water, always making certain we have enough truck and/or cargo capacity.